Dental suction lines have attached to their remote ends a disposable oral suction tip (also known as a "saliva ejector tip" or an "evacuator tip"). It is inserted into the patient's mouth for the purpose of drawing away excess fluids through the suction line. In the April 1993 edition of the Journal of the American Dental Association, Watson and Whitehouse published a paper entitled "Possibility of Cross-contamination between Dental Patients by means of the Saliva Ejector". This paper documented that, when a patient closes his or her lips around the oral suction tip, a higher vacuum can be temporarily created in the mouth than in the suction line and a back flow of fluid containing oral contaminants from the suction line into the mouth can occur.
Prior to the study by Watson and Whitehouse it had been felt that disposal and replacement of the oral suction tip between patients was sufficient protection for the patient. The study clearly showed the presence of alpha-haemolytic organisms, characteristic of oral flora, in the suction line after use. This raises the possibility of a cross-contamination occurring between patients, and demonstrates the need to re-evaluate sanitation and hygienic practises in dental offices.
The original study by Watson and Whitehouse was conducted with oral suction tips connected to low volume suction lines. A subsequent study by Watson and Whitehouse with the oral suction tips connected to high volume suction lines has determined that the back flow of oral contaminants is even more pronounced in high volume suction lines.
U.S. patent application Ser. No. 08/220,550 by Whitehouse and Watson relates to a method for preventing a back flow of oral contaminants in a suction line. The method involves placing an unregulated vacuum release aperture through a tubular sidewall of an oral suction tip. However, the method is not effective if the vacuum release aperture becomes blocked during use, and the patent contains a teaching that preventative measures should be taken to prevent such blockage from occurring.